1. Field of the Invention
The present invention relates to a complex hosel structure for a golf club head having a high degree of vibrational absorbability and elastic deformability. Particularly, the present invention relates to the complex hosel structure of the golf club head made from a two-layer complex substrate consisting of two different materials. More particularly, the present invention also relates to the complex hosel structure of the golf club head made from a multi-layer complex substrate consisting of at least two or three different materials.
2. Description of the Related Art
A conventional golf club head, as described in U.S. Pat. No. 4,995,609 entitled “Iron Golf Club Heads,” generally includes a golf club head body and a striking plate attached thereto. Typically, the golf club head body has a neck portion adjacent to a heel portion. Formed at a position below both of the neck portion and the neck portion is a recess which can relatively reduce the entire weight of the golf club head body. Accordingly, a center of gravity of the golf club head body is naturally shifted along a direction toward a side of a toe portion (opposite to a side of the heel portion). This results in a relative extension of the moment of inertia of the golf club head. In striking a golf ball, the golf club head so configured and adjusted can advantageously enhance the striking ability as well as increasing a striking distance.
Although it would be advantageous to make the recess formed on the heel portion of the golf club head body, thereby shifting the center of gravity toward the toe portion, the thinner section of the recess are susceptible to permanent distortion and inefficiencies during striking the golf club ball. Another problem with the recess of the golf club head body is raising the center of gravity upwardly in addition to shifting toward the toe portion. The primary problem with such a higher center of gravity may disadvantageously cause a relatively high sweet spot of the striking plate. Consequently, the recess of the golf club head body may be impractical and cannot improve the striking ability, as it can be a broken or permanently distorted risk during striking the golf ball. It is important to note that the design of the recess of the golf club head body cannot effectively absorb striking vibrations upwardly transmitted through the neck portion to the club shaft. On the other hand, the recess of the golf club head body cannot substantially improve its elastic deformability of the neck portion due to such a design limitation of permanent distortion.
Another conventional golf club head, as described in U.S. Patent Application Publication No. 2005/0064952 entitled “Golf Club Heads,” generally includes a golf club head body, a striking plate and a lightweight sleeve of a wrapping layer. Typically, the golf club head body has a neck portion adjacent to a heel portion. Formed on the neck portion of the golf club head body is a thin-diameter recessed section. It is advantageous that the thin-diameter recessed section of the neck portion of the golf club head body can achieve to reduce total weight, and to shift a center of gravity toward outwardly to the heel portion and downwardly to the sole portion. This results in a relative extension of the moment of inertia of the golf club head. In striking a golf ball, the golf club head so configured and adjusted can advantageously enhance the striking ability as well as increasing a striking distance. Correspondingly, formed on a front side of the golf club head body is a striking plate for striking a golf ball.
To accomplish a lower weight of the golf club head, the lightweight sleeve is made from a lightweight material to provide a low weight characteristic. In assembling, the lightweight sleeve surrounds the thin-diameter recessed section of the neck portion of the golf club head body. The lightweight sleeve can effectively enhance the structural strength of the golf club head body and absorb vibrations during striking the golf ball.
In general, the above-mentioned type of the golf club head has a number of design deficiencies, including the lightweight sleeve being only made from a single material that fails to possess a combination of characteristics of the lower center of gravity, higher vibrational absorbability and higher elastic deformability. Another design problem with manufacture of dimensions of the lightweight sleeve is the difficulty in precisely matching with dimensions of the thin-diameter recessed section of the golf club head body. To minimize a clearance between the lightweight sleeve and the thin-diameter recessed section of the golf club head body, the manufacturing operation has become difficult and sophisticated.
Another design problem with the lightweight sleeve is to provide uniform characteristics of vibrational absorbability and elastic deformability in each radial direction of the thin-diameter recessed section of the golf club head body. However, the design of the thin-diameter recessed section of the golf club head body requires the lightweight sleeve that possesses various vibrational absorbability and elastic deformability in its different radial direction according to the experimental results of the stress transmitting analysis. In other words, although it would be advantageous to install the lightweight sleeve on the thin-diameter recessed section of the golf club head body, thereby lowering the center of gravity, the one-piece member of the lightweight sleeve cannot provide various vibrational absorbability and elastic deformability in its different radial direction. Hence, there is a need for providing various vibrational absorbability and elastic deformability of the lightweight sleeve in its different radial direction for use in the golf club head according to the personal design need.
The present invention intends to provide a complex hosel structure employing two different materials for a golf club head. The complex hosel structure is constructed from a one-piece tubular member made from a two-layer or multi-layer complex substrate combined along a longitudinal direction such that the complex hosel structure has at least one first tubular, segmental wall and at least one second tubular, segmental wall. The first tubular, segmental wall of the complex hosel structure can provide a high-degree vibrational deformability characteristic while the second tubular, segmental wall can provide a high degree elastic deformability characteristic in such a way as to mitigate and overcome the above problem.